85mm lens and focus

[Tegan Payton]

Hi all.
Earlier this year, in march, I had a photo shoot with a nice local in Texas.
She used this 85 mm lens to snap a photo of my son. He had been looking at some plastic easter eggs on her window will when he turned and smiled at her. It was gorgeous. The only thing that I really noticed recently was that the side of his face that away from the camera started to blur also.

How would you mitigate that? Would you even mitigate it?

 

[astroNikon]

This is an issue of Depth of Field
Depth of Field is essentially how "deep" the "in focus" area is. or in essense the number of inches from ear to ear in this example. Depth of field, basically, is related to the aperture of the camera.

Without knowing the specifics let us just say the photographer used an aperture setting of f/2.8
In order to get more depth of field, and thus more of the total width of the face in focus, they would have to use say f/4.0 or f/5.6.

What specifically was "gorgeous" was it because only he was in focus and items in the background were out of focus? As you increase the depth of field items in the background become more and more in focus.

Thus the photographer used a small depth of field to isolate the subject, your son, in the photo. The photographer also used a little too little depth of field. But they got the image the instant it happened.

 

[Tegan Payton]

Oh thank you!

 

[snowbear]

I doubt it can be "fixed" without messing it up; it sounds like a depth of field issue.

 

[astroNikon]

This is an online article about Depth of Field ==> Understanding Depth of Field in Photography

 

[Designer]

Hi all.
Earlier this year, in march, I had a photo shoot with a nice local in Texas.
She used this 85 mm lens to snap a photo of my son. He had been looking at some plastic easter eggs on her window will when he turned and smiled at her. It was gorgeous. The only thing that I really noticed recently was that the side of his face that away from the camera started to blur also.

How would you mitigate that? Would you even mitigate it?

Another reason the shot was gorgeous is the longer focal length of the lens. Figuring the "normal" angle is around 50mm (that what it is for full-frame 35mm film size) anything shorter will introduce more distortion. A longer focal length (85 in this case) will minimize distortion, capturing facial features more like what you see in person.

Yes, I would try to mitigate it some at least so the subject's face is mostly all in focus. Knowing what to expect for DOF will help you to become a better photographer.

In order to mitigate the shallow DOF, you would use a shorter focal length lens (or zoom back), a smaller aperture, or move farther away from your subject. Or a combination of all three at once. Once you have the lens mounted, you might not want to stop everything and change lenses, but you can stop down the aperture fairly quickly, or back away some if that is enough.

You can calculate the DOF before you take the picture, knowing all of the variables involved.

 

[KmH]

What brand was the 85 mm lens, if you know?

There are quite a few online depth-of-field calculators. astroNikon linked you to 1 of them embedded in a tutorial - here is another that is standalone:
Online Depth of Field Calculator

As mentioned, using a shallow DoF is a way photographers can visually isolate a subject from the background in a portrait type photograph.
Apparently your son was close to window sill/background and the photographer had no time to make camera setting adjustments to change the DoF for the shot.

Being inside it's also likely the photographer was not using supplemental lighting and had to use a wide open aperture to get enough light into the camera. The lens aperture is one of the several factors that determine how much or how little DoF there is in a photograph.

 

[TCampbell]

Figuring the "normal" angle is around 50mm (that what it is for full-frame 35mm film size) anything shorter will introduce more distortion. A longer focal length (85 in this case) will minimize distortion, capturing facial features more like what you see in person.

Lots of good advice on "depth of field" here... but I thought I'd comment on the nature of a "normal" magnification to help understand why a lens is considered "normal", "wide angle", or "telephoto."

When you divide the focal length of a lens by the diagonal measure of the imaging chip (in millimeters), it gives you the magnification factor. We use this in astrophotography so that when we take an image with a telescope, we can determine the magnification factor of the image.

A 35mm frame (or full frame sensor) is roughly 36mm x 24mm -- yielding a diagonal measurement of about 43mm.
An APS-C sensor is (and there's a bit more wiggle room here because sizes vary by a tiny bit) around 23mm x 15mm -- yielding a diagonal measurement of about 27mm.

Everything is rounded in photography, but it means that on an APS-C camera, a 28mm lens is "normal" (1x magnification) and on a full-frame camera it's really 43mm, but nobody makes a 43mm lens. You can find 40mm and 50mm with 50mm being far more common. The 50mm is really about 1.16x magnification (just slightly better than 1x magnification) but that's close-enough so it's just rounded to 1x.

A medium-format 6cm x 6cm camera has a diagonal of about 85mm hence the 85mm is actually considered "normal" for them, but a medium format 645 camera (6cm x 4.5cm) works out to 75mm (that one is actually exact, but then nobody makes a 75mm lens so 80mm is considered the "normal" equivalent.)

 

[Derrel]

Pentax SMCP-FA 43mm f/1.9 Limited Series Autofocus Lens 20180

Rumor is that at some point in 2015 they will announce a full-frame d-slr model...

 

[Tegan Payton]

You know what, thank you all so much for all of this information!
It was a little ironic as I thought I had bought a similar lens for my new camera. I snagged a Canon EOS from ebay-- body only, for a hundred or so dollars. The guy had not used it once and had not used any of the accesories, including the photoshop (5) disk.

That being said, I also bought a used (tested, cleaned, certified, and rated) lens that I thought was 25-85mm f/2 but it is f/3.5-4.0.

Also, let's say I took her image of my son (which I won't!) and sliced the unfocused portion into another layer in photoshop, and just sharpened that layer. Would that be another workaround?

I know the point is to be a better photographer, not a subpar photographer that has to put hours of work into photoshop, in post. So, I don't intend to bonk up photos on purpose just to see.

 

[Designer]

I don't have PS, and have never tried that, but it sounds like a good solution to me.

 

[The_Traveler]

Also, let's say I took her image of my son (which I won't!) and sliced the unfocused portion into another layer in photoshop, and just sharpened that layer. Would that be another workaround?

You can't focus the OOF area enough.

 

[Tegan Payton]

Thanks!

 

[KmH]

Sharpening doesn't effect focus.
Sharpening is about edge contrast, and edge halos - Camera Lens Quality: MTF, Resolution & Contrast

Sharpening is a book length subject.
The author of this book is part of the company that wrote the Sharpening panel software used in ACR (Adobe Camera Raw/Lightroom Develop module)
Real World Image Sharpening with Adobe Photoshop, Camera Raw, and Lightroom (2nd Edition)

 

[Tegan Payton]

Sharpening doesn't effect focus."

I got out and tested my new Canon. I saw what you meant first-hand! I played with the f/settings and the mm.

I could physically see (in my viewfinder) how distance from subject and everything else interacted. I took some cute photos of my son, also!

Sadly, I was also able to see first hand that my beautiful new Canon takes a CF card, not an SD like everything else. Also, I saw that in order to communicate the photos to my computer, which doesn't have a CF slot, I would need a CF reader with a USB or the little prong-thing that hooks into the 'digital' slot on the camera. Neither of which I thought to get at Best Buy today.